To provide a device for positioning an inside cylinder by an miniaturized cylinder lock.

For the cylinder lock equipped with an outside cylinder 1 forming the inside in the shape of a cylinder and the inside cylinder 2 fitted to the cylindrical inside of the outside cylinder 1 in a rotatable manner, at the same time, having a key hole 3 inserted in the direction of the axis in an insertable manner, a click pin guide hole 9 opened in one side is formed in the inside cylinder 2 by intersecting the axis, a click pin 10 is inserted into the click pin guide hole 9 in a slidable manner and is energized toward the opening section, and an inside cylinder positioning device for the cylinder lock is so constituted that a space in which the front end of the click pin 10 can only enter is formed in a predetermined position in the circumferential direction of the inside of the outside cylinder 1.